1. Field of the Invention
The present invention relates to a USB apparatus and a USB hub apparatus. In particular, the invention relates to a USB apparatus which is connected to a host computer and transmits and receives information to and from it according to a protocol that complies with the USB standard, as well as to a USB hub apparatus which interconnects a host computer and one or more USB apparatuses and allows transmission and reception of information to be performed between them according to a protocol that complies with the USB standard.
2. Description of the Prior Art
In recent years, the reduction in the power consumption of electronic equipment has been promoted as part of various measures against the earth warming problem.
For example, personal computers or the like are constructed in such a manner that if a state that input devices (e.g., a keyboard, a mouse, etc.) are not manipulated has continued for a predetermined time or more, the personal computer automatically detects its unused state and renders a CRT (cathode-ray tube) monitor, for example, in a sleep mode to thereby reduce the power consumption.
Incidentally, in recent years, the USB (universal serial bus) has come into being as an interface for easily connecting a plurality of peripheral devices to a personal computer and now attracts much attention. Further, peripheral devices having a port for USB (hereinafter referred to as a USB port) have come to be used increasingly.
The employment of the USB enables commonization of interfaces of mice, keyboards, printers, modems, speakers, joy sticks, etc. that are separate from each other conventionally. Further, equipping a personal computer main body with only one USB port enables up to 127 peripheral devices of the above kinds to be connected to each other in star-like form if a USB hub apparatus is used.
Such an apparatus having a USB port (hereinafter abbreviated as a USB apparatus) and a hub apparatus that has a USB port and serves to connect a plurality of USB apparatuses (hereinafter abbreviated as a USB hub apparatus) are also constructed in such a manner that if they have not communicated with the host computer for a predetermined time or more, a sleep mode as mentioned above is established.
However, in such USB apparatuses and USB hub apparatuses, a USB control section, internal circuits, a preheating circuit, etc. are always supplied with power in case the personal computer restarts a transmission. This results in a problem that even if, for example, the power of the personal computer is off, a certain amount of power continues to be consumed.
The present invention has been made in view of the above circumstances, and an object of the invention is therefore to provide a USB apparatus and a USB hub apparatus which can reduce power that is consumed by the USB apparatus or the USB hub apparatus in a state that the power of a personal computer is off.
To attain the above object, the invention provides a USB apparatus which is connected to a host computer and transmits and receive information to and from it according to a protocol that complies with a USB standard, comprising power supplying means for supplying power to each section of the USB apparatus; power supply voltage detecting means for detecting presence/absence of a power supply voltage to be supplied from the host computer; and supply power control means for controlling the power that is supplied by the power supplying means in accordance with a detection result of the power supply voltage detecting means.
The power supplying means supplies power to each section of the USB apparatus. The power supply voltage detecting means detects presence/absence of a power supply voltage to be supplied from the host computer. The supply power control means controls the power that is supplied by the power supplying means in accordance with a detection result of the power supply voltage detecting means.
For example, the power supplying means supplies power to each section of the USB apparatus. The power supply voltage detecting means detects presence/absence of a power supply voltage to be supplied from the host computer via a xe2x80x9cV bus +5 Vxe2x80x9d terminal of a USB port. Referring to a detection result of the power supply voltage detecting means, the supply power control means allows the supply of power to internal circuits if the power supply voltage is supplied to the xe2x80x9cV bus +5 Vxe2x80x9d terminal, and stops the supply of power to the internal circuits if the power supply voltage is not supplied to the xe2x80x9cV bus +5 Vxe2x80x9d terminal.
Further, to attain the above object, the invention provides a USB hub apparatus which interconnects a host computer to one or more USB apparatuses and allows transmission and reception of information to be performed between the host computer and the USB apparatuses according to a protocol that complies with a USB standard, comprising power supplying means for supplying power to each section of the USB hub apparatus; power supply voltage detecting means for detecting presence/absence of a power supply voltage to be supplied from the host computer; and supply power control means for controlling the power that is supplied by the power supplying means in accordance with a detection result of the power supply voltage detecting means.
The power supplying means supplies power to each section of the USB hub apparatus. The power supply voltage detecting means detects presence/absence of a power supply voltage to be supplied from the host computer. The supply power control means controls the power that is supplied by the power supplying means in accordance with a detection result of the power supply voltage detecting means.
For example, the power supplying means supplies power to each section of the USB hub apparatus. The power supply voltage detecting means detects presence/absence of a power supply voltage to be supplied from the host computer via a xe2x80x9cV bus +5 Vxe2x80x9d terminal of a USB port. Referring to a detection result of the power supply voltage detecting means, the supply power control means allows the supply of power to internal circuits if the power supply voltage is supplied to the xe2x80x9cV bus +5 Vxe2x80x9d terminal, and stops the supply of power to the internal circuits if the power supply voltage is not supplied to the xe2x80x9cV bus +5 Vxe2x80x9d terminal.